1. Field of the Invention
The present invention is directed to novel, transient, pro-drugs useful as anti-inflammatory agents in warm-blooded animals (e.g., humans). More particularly, the present invention extends to certain novel, transient, pro-drug forms of phenylbutazone and oxyphenbutazone, known and proven anti-inflammatory agents.
For the purposes of this application, the term "pro-drug" denotes a derivative of a known and proven prior art compound (i.e., phenylbutazone and oxyphenbutazone) which derivative, when administered to a warm-blooded animal, "cleaves" in such a manner as to release the proven drug form and permit the same to attain a higher therapeutic level and/or reduced toxic action than that which could be attained if the proven drug form per se was administered.
The term "transient" denotes enzymatic and/or chemical hydrolytic "cleavage" of the compounds of this invention in such a manner that the proven drug form (phenylbutazone or oxyphenbutazone) is released and the remaining "cleaved" moiety remains non-toxic and metabolized in such a manner that nontoxic, metabolic products are produced.
2. Description of the Prior Art
Phenylbutazone and oxyphenbutazone represent non-hormonal anti-inflammatory agents, highly effective in the treatment of rheumatoid disorders and other non-specific inflammatory conditions. Chemically, phenylbutazone and oxyphenbutazone are 4-butyl-1,2-diphenyl-3,5-pyrazolidinedione and 4-butyl-2-(p-hydroxyphenyl)-1-phenyl-3,5-pyrazolidinedione, respectively.
The analgesic, antipyretic and anti-inflammatory actions of phenylbutazone and oxyphenbutazone are manifested as prompt relief of pain, lysis of fever and diminution of swelling, tenderness and local heat. The dosage regimen will vary with the size of the individual treated as well as the individual's needs. However, conventionally, an initial daily dose in adults ranges from 300 to 600 mg, divided into three or four equal doses.
While phenylbutazone and oxyphenbutazone are highly recognized anti-inflammatory agents, their respective solubilities cause extreme gastric irritation which is manifested by blood loss from the gastrointestinal (GI) tract. Essentially, phenylbutazone and oxyphenbutazone are relatively insoluble in the GI tract. In order to alleviate this situation, numerous salts and complexes of these compounds have been prepared. However, these new derivatives revert back to phenylbutazone and oxyphenbutazone, respectively, extremely rapidly in the GI tract. As a result, phenylbutazone and oxyphenbutazone are released in the GI tract (not in the bloodstream), and because of their insolubility therein, (1) they are not readily absorbed into the bloodstream, and (2) extreme GI irritation is observed. In addition, compounds specifically related to those of formula (I) above have been prepared in the past (see, U.S. Pat. Nos. 2,905,694 and 3,607,881 and Spanish Pat. No. 379,995). However, these compounds are relatively insoluble as well, and, therefore, offer no advantage over the other prior art compounds. That is, these compounds, being relatively insoluble are not absorbed readily through the GI tract. Consequently, they will not readily release phenylbutazone in the bloodstream and will not minimize GI irritation.